Supersonic fluid separation enhanced by spray injection

ABSTRACT

The separation of liquid and/or solid components from a multiphase fluid stream passing through a supersonic fluid separator is enhanced by injecting a surface active agent into the fluid stream passing through the separator. Preferably the spray is injected via an injection tube that has a positive or negative electrical potential, whereas one of the walls of the separator housing has an opposite electrical potential, so that the injected spray and any liquid droplets and/or particles formed around the injected nuclei are induced to flow towards said electrically loaded wall.

BACKGROUND OF THE INVENTION

The invention relates to a method of enhancing fluid separation in a supersonic fluid separator by injecting a spray into the fluid stream to promote nucleation of large liquid droplets and/or solid particles.

Such a method is known from Japanese patent publication JP2017921.

In the known method a seed is injected into a cyclonic fluid separator in which the fluid is accelerated to a supersonic velocity and thereby cooled to cause condensation and/or solidification of one or more components of a substantially gaseous multicomponent fluid mixture. The seed is injected downstream of a throat portion of the acceleration section to promote nucleation of large liquid droplets and/or solid particles in the fluid stream, in which a swirling motion is generated to initiate separation of a primary condensables depleted stream from a secondary condensables enriched stream by centrifugal forces.

In the known method the seed is recovered by a method of sedimentation, which indicated that the seed comprises a powder of solid particles. The method does not specify the composition of these particles.

The method according to the preamble of claim 1 is known from U.S. Pat. No. 4,141,701. In the known method a polluted air stream is accelerated to a supersonic velocity and water droplets are sprayed into the accelerated air stream to remove the pollutants.

German patent application No. DE 10040015 discloses the use of droplets comprising a surface active agent to remove pollutants from a gas.

It is an object of the present invention to provide a method wherein a spray is injected into the supersonic fluid stream, which spray comprises solid or liquid particles and/or droplets having a composition and/or electrical polarity which further enhances the separation efficiency of a supersonic fluid separator.

SUMMARY OF THE INVENTION

The method according to the present invention for enhancing the separation of liquid and/or solid components from a supersonic multiphase fluid stream comprises the step of injecting a spray comprising a surface active hydrocarbon composition into the fluid stream.

It is preferred that the surface active hydrocarbon composition predominantly comprises hydrocarbons having a carbon number between 1 and 16.

It is furthermore preferred that the spray comprises electrically laden droplets and/or particles.

In such case it is preferred that the fluid separator comprises a separation section of which at least one wall is electrically laden at an electrical polarity, which is opposite to the polarity of the electrical droplets and/or particles.

The separator may comprise a slit-shaped flow restriction in which the fluid stream is accelerated to a supersonic velocity, a slit-shaped separation section downstream of said flow restriction, a spray injection tube which injects a spray comprising electrically laden droplets and/or particles into the interior of the separator and wherein the inner surface of one of the walls of the slit-shaped separation section has an electrical polarity which is opposite to the polarity of the electrically laden droplets and/or particles.

It is preferred that the slit-shaped separation section has an upper and a lower wall and the lower wall has an electrical polarity which is opposite to the polarity of the electrically laden droplets and the upper wall has an electrical polarity which is similar to the polarity of the electrically laden droplets and/or particles.

Alternatively, the separator may be a cyclonic separator comprising an tubular upstream acceleration section, a tubular midstream section in which the fluid stream flows in a swirling motion and a downstream separation section having an annular outer outlet in which condensables enriched fluid components are collected and a tubular inner outlet in which condensables depleted fluid components are collected, and wherein the spray is injected into the interior of the cyclonic separator at a location downstream of a throat section of the acceleration section.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will be described in more detail and by way of example with reference to the accompanying drawings in which:

FIG. 1 is a schematic three-dimensional view of a supersonic fluid separator comprising slit shaped fluid acceleration and fluid separation sections; and

FIG. 2 is a schematic longitudinal sectional view of a cyclonic fluid separator in which a spray is injected to enhance the fluid separation efficiency.

Referring to FIG. 1 there is shown a supersonic fluid separator which comprises a slit-shaped acceleration section 1 and a slit-shaped separation section 2 that are arranged between profiled upper and lower walls 3 and 4 and between a pair of vertical side walls (not shown).

The profiled walls 3 and 4 define a throat section 5 in which a multicomponent substantially gaseous fluid stream 6 is accelerated to a supersonic velocity and thereby expanded and cooled and a separation section 7 downstream of the throat section 5 in which cooled and condensed components are separated from still gaseous components.

A spray 8 of a surface active agent is injected into the slit-shaped separation section 2 via small openings 10 in a spray injection tube 9 which is located just downstream of the narrowest passage of the acceleration section 1. The spray tube has a positive electrical potential so that the droplets of surface active agent also have a positive potential. The lower profiled wall 4 has a negative electrical potential in the region of the separation section 7. The droplets of surface active agent form nuclei around which condensable components form droplets and/or solid particles, which droplets and/or particles will also obtain a positive electrical potential. Thus the condensed droplets and/or solidified particles also acquire a positive electrical potential and will be attracted to the lower wall 4 that has a negative electrical potential. The droplets and/or particles will cluster together and form a liquid film or slurry at the surface of the lower wall 4, which film may flow into a slit-shaped lower condensables enriched fluid outlet passage 12, whereas the condensables depleted still gaseous components flow into a slit-shaped upper outlet passage 13, which is separated from the said lower outlet passage 12 by a flow divider 15.

FIG. 2 shows a cyclonic fluid separator which comprises an upstream acceleration section 20 in which a fluid stream 23 is accelerated to a supersonic velocity and thereby expanded and cooled, a tubular midstream section 21 comprising one or more wings 22 which induce a vortex 24 in the supersonic fluid stream and a downstream separation section 25 in which a tubular vortex finder 26 separates a central condensables depleted gaseous stream 27 from an annular condensables enriched stream 28.

A spray injection tube 30 extends through the acceleration section and injects a spray 31 of surface active lower hydrocarbons via small openings 32 into the separator. The tube 30 has a positive electrical potential so that the injected spray and any droplets and/or particles, which condense and/or solidify around the nuclei formed by the spray 31 also have a positive electrical potential. The inner surface of the tubular midstream section 21 and downstream separation section 25 have a negative electrical potential such that the positively loaded droplets and/or particles are attracted to the outer periphery of the separator interior and coalesce into a liquid film or slurry that flows along the inner surface of the separator housing into the annular condensable enriched outlet port 33.

The injection of a surface active spray which is preferably injected via an electrically loaded spray injection tube 30 and the use of a separation section having an inner surface having an electrical potential opposite to that of the spray injection tube 30 significantly enhances the separation efficiency of a supersonic fluid separator. 

1. A method for enhancing the separation of liquid and/or solid components from a multiphase fluid stream passing through a fluid separator in which the fluid stream is accelerated to a supersonic velocity and thereby cooled such that one or more condensable components condense and/or solidify, wherein a spray comprising a surface active hydrocarbon composition is injected into the fluid stream.
 2. The method of claim 1, wherein the surface active hydrocarbon composition predominantly comprises hydrocarbons having a carbon number between 1 and
 16. 3. The method of claim 1, wherein the spray comprises electrically laden droplets and/or particles.
 4. The method of claim 3, wherein the fluid separator comprises a separation section of which at least one wall is electrically laden at an electrical polarity, which is opposite to the polarity of the electrically laden droplets and/or particles.
 5. The method of claim 4, wherein the separator comprises a slit-shaped flow restriction in which the fluid stream is accelerated to a supersonic velocity, a slit-shaped separation section downstream of said flow restriction, a spray injection tube which injects a spray comprising electrically laden droplets and/or particles into the interior of the separator and wherein the inner surface of one of the walls of the slit-shaped separation section has an electrical polarity which is opposite to the polarity of the electrically laden droplets and/or particles.
 6. The method of claim 4, wherein the slit-shaped separation section has an upper and a lower wall and the lower wall has an electrical polarity which is opposite to the polarity of the electrically laden droplets and the upper wall has an electrical polarity which is similar to the polarity of the electrically laden droplets and/or particles.
 7. The method of claim 1, wherein the separator is a cyclonic separator comprising an tubular upstream acceleration section, a tubular midstream section in which the fluid stream flows in a swirling motion and a downstream separation section having an annular outer outlet in which condensables enriched fluid components are collected and a tubular inner outlet in which condensables depleted fluid components are collected, and wherein the spray is injected into the interior of the cyclonic separator at a location downstream of a throat section of the acceleration section.
 8. The method of claim 1, wherein the surface active agent comprises an organic surfactant.
 9. The method of claim 1, wherein the organic surfactant comprises molecules having a polar head and a non-polar tail. 